Pigment Deposition Research Articles

Pathologic features of anogenital precancerous high‐grade squamous intraepithelial lesion (squamous cell carcinoma in situ)

Precancerous high-grade squamous intraepithelial lesion (HSIL), the current consensus terminology for anogenital squamous cell carcinoma in situ (SCCIS), often presents with distinctive histopathologic findings that may be a function of anatomic site or associated human papillomavirus infection. Fifty-six specimens of anogenital HSIL were compared with an equal number of specimens of SCCIS from non-anogenital sites in regard to the presence of parakeratosis, flag sign in the stratum corneum, compact stratum corneum, hypergranulosis, koilocytes, small blue cells, clonal populations of keratinocytes, pagetoid scatter of atypical keratinocytes, clear cell change, glassy red cytoplasm, pigmentation, nuclear/cytoplasmic(N/C) ratio >2/1, nuclear hyperchromasia, pleomorphic nuclei, mitotic figures, abnormal mitotic figures, dyskeratotic keratinocytes, involvement of skin appendages, acantholysis and amyloid deposition. Hypergranulosis, koilocytes, small blue cells, pigmentation, nuclear hyperchromasia, dyskeratotic keratinocytes and amyloid deposition were more frequently noted in anogenital HSIL. Parakeratosis, clear cell change, pleomorphic nuclei, skin appendages involvement and acantholysis were strongly associated with non-anogenital location. There was no significant difference in the incidence of the remaining features. The strongest predicators of an anogenital location included hypergranulosis, koilocytes, small blue cells and nuclear hyperchromasia. Pigmentation and amyloid deposition were also strongly associated with an anogenital location.

How to colour a flower: on the optical principles of flower coloration.

The coloration of flowers is due to the wavelength-selective absorption by pigments of light backscattered by structures inside the petals. We investigated the optical properties of flowers using (micro)spectrophotometry and anatomical methods. To assess the contribution of different structures to the overall visual signal of flowers, we used an optical model, where a petal is considered as a stack of differently pigmented and structured layers and we interpreted the visual signals of the model petals with insect vision models. We show that the reflectance depends, in addition to the pigmentation, on the petal's thickness and the inhomogeneity of its interior. We find large between-species differences in floral pigments, pigment concentration and localization, as well as floral interior structure. The fractions of reflected and transmitted light are remarkably similar between the studied species, suggesting common selective pressures of pollinator visual systems. Our optical model highlights that pigment localization crucially determines the efficiency of pigmentary filtering and thereby the chromatic contrast and saturation of the visual signal. The strongest visual signal occurs with deposition of pigments only on the side of viewing. Our systematic approach and optical modelling open new perspectives on the virtues of flower colour.

Agouti signalling protein (ASIP) gene: molecular cloning, sequence characterisation and tissue distribution in domestic goose

Agouti signalling protein (ASIP) is an endogenous antagonist of melanocortin-1 receptor (MC1R) and is involved in the regulation of pigmentation in mammals. The objective of this study was to identify and characterise the ASIP gene in domestic goose.The goose ASIP cDNA consisted of a 44-nucleotide 5ʹ-terminal untranslated region (UTR), a 390-nucleotide open-reading frame (ORF) and a 45-nucleotide 3ʹ-UTR. The length of goose ASIP genomic DNA was 6176 bp, including three coding exons and two introns.Bioinformatic analysis indicated that the ORF encodes a protein of 130 amino-acid residues with a molecular weight of 14.88 kDa and an isoelectric point of 9.73.Multiple sequence alignments and phylogenetic analysis showed that the amino-acid sequence of ASIP was conserved in vertebrates, especially in the avian species.RT-qPCR showed that the goose ASIP mRNA was differentially expressed in the pigment deposition tissues, including eye, foot, feather follicle, skin of the back, as well as in skin of the abdomen. The expression level of the ASIP gene in skin of the abdomen was higher than that in skin of the back.Those findings will contribute to further understanding the functions of the ASIP gene in geese plumage colouring.

Brown-McLean syndrome: the role of iridodonesis.

PurposeThe aim of this study was to report a case series of Brown–McLean syndrome (BMS).MethodsThe charts of 28 patients with BMS at Ramathibodi and Rutnin Hospital from 1981 to 2015 were reviewed.ResultsBMS is a rare condition with corneal edema involving the peripheral cornea with orange-brown pigment deposition underlying the edematous area. The edema typically starts inferiorly and advances circumferentially to superior cornea. Central cornea remains clear in most patients. We report 28 patients with BMS that occurred either spontaneously or after various intraocular procedures. Ultrasound biomicroscopy was performed to demonstrate the iridocorneal relationship.ConclusionIridocorneal relationship from the ultrasound biomicroscopy study in four patients did not support previous hypothesis about the role of iridodonesis impact on corneal endothelium. Patients with BMS can rarely progress to corneal decompensation; however, they should be periodically monitored and made aware of early clinical signs of their complications.

The pugilistDominant Mutation of Drosophila melanogaster: A Simple-Sequence Repeat Disorder Reveals Localized Transport in the Eye.

The pugilist-Dominant mutation results from fusion of a portion of the gene encoding the tri-functional Methylene Tetrahydrofolate Dehydrogenase (E.C.1.5.1.5, E.C.3.5.4.9, E.C.6.3.4.3) to approximately one kb of a heterochromatic satellite repeat. Expression of this fusion gene results in an unusual ring pattern of pigmentation around the eye. We carried out experiments to determine the mechanism for this pattern. By using FLP-mediated DNA mobilization to place different pugD transgenes at pre-selected sites we found that variation in repeat length makes a strong contribution to variability of the pug phenotype. This variation is manifest primarily as differences in the thickness of the pigmented ring. We show that similar phenotypic variation can also be achieved by changing gene copy number. We found that the pugD pattern is not controlled by wingless, which is normally expressed in a similar ring pattern. Finally, we found that physical injury to a pugD eye can lead to pigment deposition in parts of the eye that would not have been pigmented in the absence of injury. Our results are consistent with a model in which a metabolite vital for pigment formation is imported from the periphery of the eye, and pugD limits the extent of its transport towards the center of the eye, thus revealing the existence of a hitherto unknown mechanism of localized transport in the eye.

The transcription factor VpCRZ1 is required for fruiting body formation and pathogenicity in Valsa pyri

Valsa pyri is a fatal pathogenic fungus that causes pear and apple canker disease. To date, its cellular development and pathogenicity have been poorly understood. In this study, a V. pyri Ca2+/calcineurin-dependent transcription factor CRZ1 (VpCRZ1) is identified and functionally characterized. The △VpCRZ1 mutant exhibits impaired pathogenicity and is no longer able to form fruiting body. Interestingly, this mutant also exhibits enhanced pigment deposition and increased resistance to cell wall perturbing agents including SDS, Congo red and calcofluor white (CFW). The expression levels of Congo red resistance genes (VpRCR1 and VpRCR2) and chitin synthetase genes (VpCHS2 and VpCHS6) are upregulated in the △VpCRZ1 mutant compared to the wild type. Furthermore, We show that a VpCRZ1: eGFP fusion protein localizes to the nucleus in a Ca2+-dependent manner similar to its homologs in other fungi, and that the VpFKS1, VpPMC1, VpPMC2, VpPMR1, and VpPMA1 genes are regulated by VpCRZ1 in response to Ca2+ levels. Together, these results suggest that VpCRZ1 is a Ca2+-dependent transcription factor and required for regulating mycelial morphology, fruiting body formation, and virulence of this important pear and apple pathogen.

How to reduce the costs of ornaments without reducing their effectiveness? An example of a mechanism from carotenoid-based plumage.

Carotenoid-based ornaments are often considered to be honest indicators of individual quality assessed by potential mates. However, males can use a variety of strategies that minimize the amount of costly carotenoids used while retaining the effectiveness of color signaling. Birds could do this by altering pigment intake, metabolism, or its presentation to a potential signal receiver. Here, we propose a new mechanism of lowering the costs of carotenoid displays in birds: differential allocation of pigments within single feathers. We studied the coloration of the yellow terminal tail bands of rectrices of male Bohemian waxwings. Using reflectance spectrometry, we show that the two central rectrices are most intensively colored compared to other rectrices. More detailed analyses reveal that these differences result from feather-specific patterns of rectrices coloration. The outer feather vanes of the outermost rectrices are more intensively colored compared to the inner vanes. However, the central rectrices have equally colored vanes that are, on average, more intensively pigmented than the outermost rectrices. When the waxwing tail is folded, the outermost rectrices are covered by other feathers, except for the narrow, outer vane. Central rectrices, however, form the outermost layers which are not obscured by other tail feathers. Thus, the feather vanes that are the most visible to potential viewers are also the most pigmented. These results support the occurrence of a previously overlooked mechanism to reduce the costs of carotenoid-based ornaments: precise pigment distribution to maximize efficiency of signals within single feathers.Significance statementMales of many bird species use bright carotenoid-based plumage coloration to attract females. These traits are physiologically expensive such that only individuals in prime condition can develop the most vivid colors. Males often “cheat” to obtain attractive appearances at lower costs. We showed that this goal could be achieved by differential deposition of pigments into the most conspicuous feather regions. Bohemian waxwing males have yellow tips on their rectrices of which the outer vanes are more brightly colored compared to the inner vanes. These inner feather vanes are usually covered by other feathers and are, thus, less visible to conspecifics. The only exception is the pair of central rectrices that are fully exposed, and both feather vanes are equally colored. In this species, males minimize the use of costly carotenoid pigments while maintaining elaborate ornamentation of plumage regions that are most visible to potential mates.

Autosomal recessive retinitis pigmentosa with homozygous rhodopsin mutation E150K and non-coding cis-regulatory variants in CRX-binding regions of SAMD7.

The aim of this study was to unravel the molecular pathogenesis of an unusual retinitis pigmentosa (RP) phenotype observed in a Turkish consanguineous family. Homozygosity mapping revealed two candidate genes, SAMD7 and RHO. A homozygous RHO mutation c.448G > A, p.E150K was found in two affected siblings, while no coding SAMD7 mutations were identified. Interestingly, four non-coding homozygous variants were found in two SAMD7 genomic regions relevant for binding of the retinal transcription factor CRX (CRX-bound regions, CBRs) in these affected siblings. Three variants are located in a promoter CBR termed CBR1, while the fourth is located more downstream in CBR2. Transcriptional activity of these variants was assessed by luciferase assays and electroporation of mouse retinal explants with reporter constructs of wild-type and variant SAMD7 CBRs. The combined CBR2/CBR1 variant construct showed significantly decreased SAMD7 reporter activity compared to the wild-type sequence, suggesting a cis-regulatory effect on SAMD7 expression. As Samd7 is a recently identified Crx-regulated transcriptional repressor in retina, we hypothesize that these SAMD7 variants might contribute to the retinal phenotype observed here, characterized by unusual, recognizable pigment deposits, differing from the classic spicular intraretinal pigmentation observed in other individuals homozygous for p.E150K, and typically associated with RP in general.

Eggshell biliverdin concentration does not sufficiently predict eggshell coloration

Avian eggshell coloration may have arisen due to selection on the biological, chemical, or physical properties of the pigments embedded within the eggshell, or due to selection on the coloration that emerges due to pigment deposition. Within both hypothetical frameworks, pigment‐based eggshell coloration would be related to metrics of egg quality; however, no one has evaluated the relative strength of coloration and pigment concentration in predicting egg quality. Here, we examined 66 European starling Sturnus vulgaris eggs and quantified eggshell biliverdin concentration (an antioxidant that produces the eggshell's blue coloration) and used 28 different coloration metrics derived from both photographic and spectrophotometric data. We also measured egg size, eggshell thickness, concentration of carotenoids in the yolk, and concentration of lysozyme in the albumen to capture variation in egg quality. We found that throughout the laying sequence, biliverdin concentration increased while eggshell thickness, yolk carotenoid concentration, and lysozyme concentration in the albumen all decreased, but this variation was not captured by any eggshell coloration metric. Both eggshell coloration and biliverdin concentration were negatively associated with yolk carotenoid concentration, but only eggshell biliverdin concentration was negatively associated with yolk mass. Lastly, biliverdin concentration explained, at most, only 46% of the variation for all eggshell coloration metrics. Our results suggest biliverdin concentration is a better predictor of egg quality than egg coloration in European starlings, supporting the hypothesis that eggshell pigment concentration per se may be the target of selection.

A β-solenoid model of the Pmel17 repeat domain: insights to the formation of functional amyloid fibrils.

Pmel17 is a multidomain protein involved in biosynthesis of melanin. This process is facilitated by the formation of Pmel17 amyloid fibrils that serve as a scaffold, important for pigment deposition in melanosomes. A specific luminal domain of human Pmel17, containing 10 tandem imperfect repeats, designated as repeat domain (RPT), forms amyloid fibrils in a pH-controlled mechanism in vitro and has been proposed to be essential for the formation of the fibrillar matrix. Currently, no three-dimensional structure has been resolved for the RPT domain of Pmel17. Here, we examine the structure of the RPT domain by performing sequence threading. The resulting model was subjected to energy minimization and validated through extensive molecular dynamics simulations. Structural analysis indicated that the RPT model exhibits several distinct properties of β-solenoid structures, which have been proposed to be polymerizing components of amyloid fibrils. The derived model is stabilized by an extensive network of hydrogen bonds generated by stacking of highly conserved polar residues of the RPT domain. Furthermore, the key role of invariant glutamate residues is proposed, supporting a pH-dependent mechanism for RPT domain assembly. Conclusively, our work attempts to provide structural insights into the RPT domain structure and to elucidate its contribution to Pmel17 amyloid fibril formation.

Pathologic Alterations of Canine and Feline Adrenal Glands

The aim of the study was to determine the frequency and age-dependency of adrenal changes in dogs and cats, which were dissected between 2004 and 2006 at the Institute of Veterinary Pathology, LMU Munich. The adrenal glands of 101 dogs and 159 cats were dissected free from adjacent tissue, weighed, lamellated perpendicular to its longitudinal axis and were embedded in paraffin and plastic for histologic inspection. Ageing cats most frequently showed accessory cortical nodules in the capsule, cortex and medulla, pigment deposition and shock bodies. The appearance of accessory cortical nodules and pigment deposition were linked to the age of the cats and that of shock bodies was linked to infectious diseases. Inflammatory alterations were rare and neoplastic changes were not observed. In dogs, the most frequent alterations were accessory cortical nodules in the capsule, cortex and medulla and circulatory disturbances and there was a significant linkage of the appearance of cortical nodules and pigment deposition and age. Metabolic, inflammatory and tumorous diseases were rarely observed in the dogs examined. In summary, cats and dogs show similar incidental alterations of the adrenals. Clinical relevant adrenal lesions such as atrophy or primary neoplasia were rarely diagnosed.

Cardiac stroke following total knee replacement in an ochronotic arthropathy: Case report and literature review

Alkaptonuria is a rare autosomal recessive disorder caused by defective metabolism of homogentisic acid (HGA) which on accumulation in the connective tissues causes arthritis, darkening of urine and connective tissue pigmentation. Knee is most commonly affected joint whereas pigment deposition is seen in entire body causing cardiovascular, genitourinary, ocular, cutaneous, and musculoskeletal complications. We here report such a case of bilateral ochronotic arthropathy, who was diagnosed to be alkaptonuric only during joint exploration. He sustained a cardiac catastrophic stroke on 3 rd post operative day of the left knee replacement which was done one week after the right knee replacement. With prompt treatment and good hospital care, the patient was revived successfully, without valvulotomy or valvular replacement. The spectrum of clinical manifestations are discussed in the report with emphasis on thorough history and clinical examination of the patient, before taking the patient to the total knee replacement to make accurate diagnosis before hand and be prepared for the complications or catastrophic by a multidisciplinary approach.

Identification of an amyloid fibril forming segment of human Pmel17 repeat domain (RPT domain).

Pmel17 is the major component of functional amyloid fibrils that have an important role during pigment deposition. Pmel17 polymerization is promoted within the mildly acidic conditions of melanosomes, organelles located in pigment-specific cells. A repeat domain (RPT domain) of Pmel17, rich in glutamic acid residues has been extensively associated with the formation of the fibrous matrix. Here, we examine the RPT domain of human Pmel17 in order to provide information on this mechanism. Specifically, we have identified an aggregation-prone peptide segment ((405) VSIVVLSGT(413) ), close to the C-terminal part of the RPT domain. Experimental results utilizing electron microscopy, X-ray fiber diffraction, Congo red staining and ATR FT-IR spectroscopy indicate that this peptide segment self-assembles forming fibrils with evident amyloidogenic properties. Conclusively, our results demonstrate that the (405) VSIVVLSGT(413) peptide segment possibly has an essential role in RPT domain fibrillogenesis.

Prevalence of ocular pseudo exfoliative syndrome in rural population: A study from South India

Introduction: Pseudo-exfoliation is a complex age related disorder of production and accumulation of fibrillar material in the anterior segment of eye.It is more common as the age advances. It is also associated with serious ocular problems such as cataract and glaucoma. Aims: To find out the prevalence and pattern of clinical presentation in pseudo-exfoliative syndrome in patients visiting ophthalmology out- patient department in a rural area. Materials and Methods: This was a prospective study carried out over a period of one year in the department of Ophthalmology, Mamata Medical College and associated General Hospital, Khammam. In this study 2000 individuals, (1111 male and 889 female) above the age of 40 years, were selected randomly and complete ocular examination was done in these subjects. Results: Ninety (4.5%) out of 2000 individuals screened showed varying degree of pseudo-exfoliation syndrome in one or both eyes. The prevalence rate increased with advancing age. It was 4.5%, at 40 years and above, 5.35 %, 6.35 % and 6.89 % at 50, 60, and 70 years and above respectively. In males the prevalence rate was 5.67% and in females 3.03%. Mean age at which this syndrome was detected is 67.32 SD±8.81 years. In males, it was 68.84 (SD±8.26) years and in females 63.96(SD±9.20) years. Bilateral involvement of the eyes was more common. Frequency of signs of pseudo- exfoliation syndrome increased with advancing age and the common signs were pseudo-exfoliation material over pupillary border, over anterior capsule of lens, peripheral band, pupillary ruff defects, pigment deposition over trabecular- meshwork and over endothelial surface of cornea, and on anterior surface of lens capsule. Conclusion: Pseudo-exfoliation syndrome is common in hospital visiting population especially in the elderly population in rural South India. Thorough ophthalmologic examination helps to pick up this syndrome. Early detection helps to prevent associated complications such as cataract, g

Patho-Surveillance and Pathology of Fascioliosis (Fasciola gigantica) in Black Bengal Goats in Bangladesh

The aim of the study was conducted to investigate patho-surveillance and pathology of fascioliosis in Black Bengal goats in Sylhet region of Bangladesh. Patho-surveillance and Pathology on fascioliasis of Black Bengal goats were undertaken in such localities under different climatic conditions existing in Sylhet region of five different Upazilla. Goats were divided into young and adult groups. Affected liver samples from slaughtered goats were collected randomly and examined by grossly and histopathological study for hematoxylin and eosin staining. A total of 2000 Black Bengal goat livers were examined, of which 202(10.10%) livers were found to be affected with fascioliosis. Prevalence of fascioliosis was significantly higher in young goats (15.58 %) than in adult (9.59%) and female goats (13.10%) were more susceptible than male goats (7.10%). Seasonal prevalence of fascioliosis was also studied. Highest prevalence (16.51 %) was recorded during rainy season and lowest prevalence (4.70%) was recorded during summer season. Grossly, affected livers were enlarged with rounded edges and thickened capsule. In acute cases, numerous haemorrhagic spots were found on the parietal & visceral surfaces of the affected liver. In chronic form, liver was cirrhotic and reduced in size. The affected intra-hepatic bile ducts were protruded and engorged with flukes. Microscopically, migratory tracts were represented by the presence of haemorrhage, edema and infiltration of numerous eosinophils mixed with few lymphocytes. Fatty change, atrophy and necrosis of hepatocytes were recorded along with deposition of bile pigment in hepatic parenchyma and damage of portal tract area. The wall of bile ducts was thickened due to fibrosis and lining epithelia were hyperplastic. Cross sections of adult and immature flukes were found within the lumen of the thickened bile ducts and hepatic parenchyma respectively. The study to provides valuable in insight towards better understanding of epidemiology and pathogenesis of the disease in Black Bengal goats to adopt suitable control strategies against the disease and meat inspection at slaughter houses.

Exogenous ochronosis treated with CO2 Laser

Exogenous Ochronosis is a rare skin disease. It is usually associated with the topical use of hydroquinone, resulting in a grayish or bluish black hyperpigmentation due to dermal deposition of ocher pigment. There is no gold standard treatment and the therapeutic options are generally not effective. We report a case of a patient with exogenous achronosis after use of Hydroquinone, treated with CO2 Laser and showing very good results

Difficult epidural in a patient with undiagnosed alkaptonuria.

Sir, Endogenous ochronosis or alkaptonuria is an extremely rare autosomal recessive inborn error of amino acid metabolism which was described by Garrod in 1901.[1] It occurs due to the absence of the enzyme homogentisate 1,2-dioxygenase that converts homogentisic acid to maleylacetoacetic acid in the process of tyrosine metabolism.[2] We wish to highlight difficulties faced in securing neuraxial anaesthesia in an undiagnosed case of alkaptonuria and the significance of identifying mucocutaneous markers of ochronosis which can be missed in dark-skinned Asian patients. A 69-year-old male, who presented with pain in both the knee and hip joints and no significant comorbidity, was posted for total replacement of the right hip joint, with a provisional diagnosis of osteoarthritis. General physical examination showed bilateral pigmented keratinised lesions on the palmar aspects and outer edges of his fingers [Figure 1a]. His vital parameters were stable and systemic examination was unremarkable. Airway examination revealed a mild restriction of neck extension and Malampatti class 3. The lumbar interspinous spaces were not distinctly felt. The electrocardiogram showed an incomplete right bundle branch block and the echocardiogram showed a degenerated sclerotic aortic valve, trivial regurgitations in the mitral and tricuspid valves and a normal left ventricular ejection fraction. Combined spinal–epidural anaesthesia was planned. Figure 1 (a) Greyish-blue, pitted, scaly and non-itchy lesions on the palms. (b) Greyish scleral pigmentation Lumbar epidural needle insertion was attempted long the midline but failed as bone was encountered with repeated attempts. The patient was then positioned on the right lateral side with the affected joint dependent and subarachnoid block through a paramedian approach was successful. The epidural space was reached after multiple attempts by the paramedian approach near L2-3 and an 18 gauge epidural catheter was successfully threaded into space. Intra-operatively, the surgeon alerted us regarding the dark colour of the cartilage around the hip joint. Ochronosis was then implicated to be the cause of arthritis and the difficulty in securing neuraxial anaesthesia. Close evaluation of the eyes revealed pigmented lesions bilaterally [Figure 1b] and the ears were found to be hard and thickened. The lumbar spine radiograph obtained subsequently showed calcification of the intervertebral discs [Figure 2a]. The urine was tested which turned dark after a few hours on exposure to air and further on alkalinisation [Figure 2b]. Histopathological evaluation of the femoral head confirmed the diagnosis [Figure 2c]. The patient later recollected that his unwashed underwear showed ash-coloured stains. Figure 2 (a) Intervertebral disc calcification (yellow arrows). (b) Change in the urine colour on alkalinisation and exposure to air. (c) Microscopic pigment deposition in the cartilage and in the synovium Since the disease often presents in the later decades of life with symptoms closely resembling other arthropathies, the diagnosis is often missed. Anaesthesiologists encounter these patients when they are posted for replacements of the hip or knee joints and for spine surgeries. They can present with ochronotic spondyloarthropathy with decreased range of movements of the spine and hips, facet joint degeneration, spinal canal stenosis and pseudo ankylosis of the cervical joints, reduced intervertebral disc spaces and dense disc calcification that can result in difficult neuraxial anaesthesia as well as intubation.[3,4] Bilaterally symmetrical scleral pigmented lesions, as seen in our patient, should rouse suspicion of an underlying systemic cause.[5] Greyish-blue, pitted, non-itchy, scaly lesions on the edges and palmar aspects of the hands, greyish discolouration of the ear pinna and stiff and hard helical cartilage were noted in our patient can easily be missed.[6] Calcifications in the coronaries, cardiac valves and aortic root, urinary pigment calculi and nephrotoxicity may be significant enough to alter anaesthetic management.[2] Although surgical implications are minimal, surgeons should involve the anaesthesiologist, physician and cardiologist early in the pre-operative period to establish a well-planned management approach. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

A novel R2R3-MYB transcription factor regulates light-mediated floral and vegetative anthocyanin pigmentation patterns in Lilium regale

Color patterns in angiosperm flowers are produced by spatially and temporally restricted deposition of pigments. Many Lilium species show anthocyanin pigmentation of the whole tepal, which is regulated by the MYB12/basic helix-loop-helix 2 (bHLH2) transcription factor complex. However, in Lilium regale pigment deposition is restricted to light-exposed surfaces of the flower buds, leaves, and bracts. Investigation of how the unique color patterns of L. regale are regulated led to the identification and isolation of a novel R2R3-MYB gene, LrMYB15. In stable and transient transformation assays in tobacco, LrMYB15 stimulated transcription of anthocyanin biosynthesis genes, indicating that it is involved in the positive regulation of anthocyanins. In L. regale, anthocyanin biosynthesis genes and LrMYB15 were expressed in the outer tepals, leaves, and bracts that accumulated anthocyanin pigments. In contrast, LrbHLH2, another regulatory gene for anthocyanin biosynthesis, was transcribed in all organs irrespective of anthocyanin accumulation. These results indicate that LrMYB15 principally determines the unique anthocyanin color patterns of L. regale. In addition, LrMYB15 transcription ceased completely when plants were kept in shaded conditions and the colors of the flower buds faded, indicating that transcription of this gene is under the control of light. R2R3-MYB genes that regulate light-induced anthocyanin accumulation on exposed petal surfaces have been isolated in eudicots. The results here indicate that R2R3-MYB genes exhibiting similar (but not identical) functions are conserved between monocots and eudicots and that transcriptional regulation is a major mechanism for generating restricted pigment deposition in the flowers of a wide range of angiosperm species.

Regulatory mutations in TBX3 disrupt asymmetric hair pigmentation that underlies Dun camouflage color in horses.

Dun is a wild-type coat color in horses characterized by pigment dilution with a striking pattern of dark areas termed primitive markings. Here we show that pigment dilution in Dun horses is due to radially asymmetric deposition of pigment in the growing hair caused by localized expression of the T-box 3 (TBX3) transcription factor in hair follicles, which in turn determines the distribution of hair follicle melanocytes. Most domestic horses are non-dun, a more intensely pigmented phenotype caused by regulatory mutations impairing TBX3 expression in the hair follicle, resulting in a more circumferential distribution of melanocytes and pigment granules in individual hairs. We identified two different alleles (non-dun1 and non-dun2) causing non-dun color. non-dun2 is a recently derived allele, whereas the Dun and non-dun1 alleles are found in ancient horse DNA, demonstrating that this polymorphism predates horse domestication. These findings uncover a new developmental role for T-box genes and new aspects of hair follicle biology and pigmentation.

Bilateral acute iris transillumination: Case report

Bilateral acute iris transillumination (BAIT) is a recently defined disease characterized with bilateral acute, severe pigment dispersion of iris and pupil sphincter paralysis. The etiopathogenesis of the disease is unknown, but antibiotics such as moxifloxacin, clarithromycin, viral infections, and fumigation therapies were considered as probable etiologic factors. A 33-year-old female was referred to our clinic for acute iridocyclitis refractory to azathioprine, colchicum and corticosteroid treatments. Ophthalmic examination revealed bilateral pigment dispersion, significant iris transillumination, heavy pigment deposition in iridocorneal angle, and elevated intraocular pressure. Upon systemic evaluation she was found to have bacterial urinary tract infection. BAIT is an important cause of pigment dispersion and clinicians must be vigilant for this condition to avoid unnecessary diagnostic tests and treatment.